In semiconductor technology, methods for temporary bonding are playing a more and more important part to be able to optimally handle structure wafers which are becoming thinner and larger in area. The handling of structure wafers in the prior art has been especially improved by only one part of the structure wafer being temporarily bonded to the carrier wafer, preferably a peripheral edge. In this way contact of adhesive with the structured side of the structure wafer is avoided as much as possible. This is achieved in the prior art by only one edge zone of the coating surface of the carrier wafer being made adhesive, in particular by an inner circular surface of the wafer being coated with a coating material which reduces the adhesive force. A nonadhesive coating material is preferably, but not restrictively, an Anti Sticking Layer Material (ASL) such as for example EasyClean Coat 1000 from 3M.
The prior art has instantaneously following steps for production. First the edge zone B of a carrier wafer is coated with a resist, for example a photoresist. The photoresist is cured in a furnace or on a heating plate. Afterwards an ASL is applied over the entire surface. The ASL material cannot reach the surface of the carrier wafer which has been covered by the photoresist. After a certain action time in which a molecular layer has formed on the central region of the carrier wafer which is not covered with the photoresist, the remaining ASL material is spun off. Afterwards the photoresist is removed, for example with acetone. At this time the carrier wafer consists of two zones, one edge zone without ASL coating and a core zone with ASL coating. Afterwards an adhesive is applied on the entire carrier wafer. The adhesive adheres very well to the edge zone which has not been covered with ASL material. The adhesive strength of the adhesive in the core zone which has been coated with ASL material is very low. The cement is used in this core zone mainly to support structures of the structure wafer which is to be bonded later to the carrier wafer. It is clearly apparent from the prior art that several steps are required for producing the two zones. First, the application of the photoresist, second the curing of the photoresist, third the application of the ASL material, fourth the removal of the photoresist, and fifth the application of the adhesive.
The application of the coating and of the adhesive to the carrier wafer will take place as economically and quickly as possible, but at the same time in high quality, therefore especially a layer thickness as uniform as possible.